Hardness calculating device



- HRDNESS GALCULA/TING DEVICE Filed Jlily l'4 1942 JOHN CHRIS TOPHER CLIFTON E53 mm" WW /l Y H M f5 Patented Jan. 8, 1946 Unirse .fisuras YATE NT CQ'FQF HARDNESS 'CALCULATINGADEVICE v`Application gJuly "14, 1942,SerialNo. 450,944 ""lnfGreat Britain July 1"0,1\941 3 Claims.

"This invention relates to 'apparatus 'for the-direct numerical evaluation of hardnessnumerals from the observation of ,impressions -`made *by means of a-penetrometer under -"various values of loading.

`^v'The object 'of the invention "is tojprovide apparatusgwherebyithenumerical value of the hardness 'can be directly read off ron a scaleforming part of the apparatus, by measurementoftheimpression made v*by thepenetrometer, and further so to construct the measuring apparatus, that thisdirect'reading is established Yeven though the conditions Aof nobservation of such impression,` and also theconditions which ,producefit-are varied separately 'or collectively. It willbe appreciated that the direct reading provided bythe apparatus, which isthe subject lof the kpresent invention may, if desired, ``be optically transferred to Aa screen, or `otherwise suitably disposed for reading `Vthe recorded Valueseither separately from, or in vconjunction lwith, the optical imajge of Vthe visual mark'being measured.

Accordingto .the invention, 4,the apparatusjfor the direct numerical evaluation of 'hardness 'from the observation ofan impression ,made on metals under-a definite load 'by-'means ofjpenetrometer under specied conditions, comprises two axially mountedvtranspaitentdiscs. One o'ffthe discs is suitably inscribed-with Vlogarithmic scales of corresponding Vvalues of theload and the `hardness for a constant given size ofiimpressiomthe other disc with-a-double-sided veoluiangular` logarithmic spiral, the 4angular distances from agiven origin representing, 'on 4a logarithmic scale the areas of the impression, or'the squares of valinear dimension of the impression, i. e..diameter 'of a circular impression, for diagonal of a usquare impression, or I the like, which A dimension determines the size of 'the surface ,of -the impression. 'The segments of the radii'- between vthe sides of the spiralrepresentthe lengths'or a `constant multiplerof the lengths of ysaid determining linear dimension. The -dises areadapted vto 'be pivotally Vdisplaced against -each Vother Aforpbringng said scales ,on the'one'o'f `said-discs and said spiral onr the other of :said discs -to a definite vangular relationship depending ontheA load Which-,was used when making theimpression. The doublesided equiangular logarithmic spiral -is adapted to .caliper said determining linear dimension, the` ealipering Aangular'position l then indicating ,on the hardnessv scale the hardness value -of ithe metal on which the impression-had been made.

AfIn vorder that-'the inventionmay' be morel clearly understoodfthe same 'will now be "described with reference lto the "accompanying diagrammatic drawingin which:

Figure `1'shows'one"moVableelementy of "the *apparatus,

Figure 2'shows'theesecond movable element,

Figure 3 illustrates thejgeneralarrangement Yof the apparatus and associated `-proj ect-ion systems, Figure -4 "isa plan view heorresponding'fto Figure 3. k For the purpose lof vevaluating hardness -numera-1s itisneoessary Vin order 4to obtain-'satisfactory conditions o'f `test to makef'observations of 4impressionsA made Vunder different `values -of loading and -magnication'and-it has been establishedA that the hardness -numeral varies 4vdirectly as-the load used to -makethe Vimpressionand inversely asthe squareof the linear dimensions of--the impressionv produced. `IfL is the 1ioacL'f-lta linear dimension ofi-the impression "determining the ysize of yits surface, y'such as, "if -circular "its diameter, or if square rits diagonal, Hjthe'hardness, and C a constant,-then From this `form `of 'the mathematical 'relation between the variables 1L, d,'H, follows that when all variables are varying together, the logarithm of the hardness 'number -is always equal to fthe logarithmof the load, minus'twice the-logarithm of the 'determini-ng linearfdimension of thai-mpression, plus a constant:

slidable V:against each other, comparable to ar logarithmic-slide ruleglogarithmic :scales of f=cor responding vvalues of theloadand o'fi the hardness and 'on theother `an appropriate :representation of twice the logarithms ofthe determininglflinear dimension, "we, by displacing .the vtwo elements relatively .to eachother, or'bybringing theilogarithmic representationof the ,values d linfa 'denite-spatialrelationship to .theload scale depending :on .the value oftheload used,1mayrevaluate the value of the variable Hfrom any value of the determining linear dimension d of the impression. If vin .the second element, by the `use Yof Van optical ,system in the apparatus, a magnified image of the impression is used insteadof "the impression itself, the" linear dimension dA will-appear magnied to D, the factor of the linearmagnication being m, (D=md), Equation f 2 Vwill read:

=log H='logL-2log D+2 log m-l-logfc '(3) thatmeans lthat in order to obta'inthe hardness number at a given load and a given size of the impression, the displacement of Vthe second element is to be rdiminished by a displacement cor-A responding to the value of the magnification or 2 log m.

As elements' slidable against each other, We Y employ two circular discs I and 2, respectively illustrated in Figs. l and 2. The discs are rotatable about a common axis III-4I, Fig. 3, passing normally through their geometric centres.

Y On the first disc I there are inscribed'two circular scales 2l, 28, the outer scale 21 preferably being used for the hardness numbers and theV inner scale 28 for the loads. 1 y u VSince the variables H, L, d and the optical magnication of the image used to observe and measure the impression, comprise all the variable factors involved, the scales on disc I may be laid out in the following manner:

For a constant size of impression the hardness Anumeral is directly proportional to the load.

Starting therefore from chosen initial conditions, this relation will give corresponding values of thesetWo-variables, when the size of impression and magnification remain constant.

Vangular spacing of these radii willin general depend upon thek mathematical form of the ex-A pression connecting all the variables, and in the present case will be distributed around the circumference, from ja suitable initial value of the loadffrorn an origin indicated at 30 and 3l respectively, over the-requiredY range, withV the anlgles proportional to the logarithms of the load and hardness number values. y The second circular disc 2 is mounted concentrically with, but independently of, the disc I previously described, the diameter-of the disc 2 being .preferably somewhat smaller than that of discfI. Thesecondmovable disc is also preferablymade'of transparent material.Y Y

This Vsecond element serves -as a caliper, prefimage optically transferred to a screen, the initial optic axisV of the system passing normally through the centre of the impression, and also normally to the faces of the two movable disclike elements, The lines 32, 33 inscribed on the second movable element, in the manner about to be described, are situated directly against the impression, as Fig. 4 illustrates at II2, and the portions of the field of view are in focus as well ness expressed by a given hardness'number, the

area of the impression or the squarefof the linear dimension of the impression varies directly as the load, that is, twice the logarithm of the linear dimension varies as the logarithm of the load.

0n any radius such as 44, Fig. 2, which hereinafter I shall term origin of the disc, andA symmetrically about theV imaginary circumference 24 defined above there are laid out, as indicated by 45,' 46, respectively, thegreatest and least values, over the required range, of the most convenient linear dimensions of the impression or its image,

usually multiplied by a suitable magnification factor in accordance with. the magnification. of the optic sys/tem employed. Intermediate values areV now laid down radially, with the angles proportional'to the logarithms of these values.

The result of this process is that the disc has been inscribed with a double sided, equiangular logarithmicV spiral 32, f 33 symmetrically Ydisposed about the circumference 34 passing through the centre line ofthe impression l2 or its projected imageV II2. This spiral33, 34, which is used to Y registeragainst the impression. IZYorits image erably an optical caliper, which measures the im-V pression. Simultaneously, the second member serves 'as the second member of acircular logarithmicslide rule which in the calipering angular position shows the hardness number sought.

We inscribe therefore on this element the vary- 'ingisizes of the'impression, and since, as a rule, a magnied image of the impression is .projected on' this element by optical means, we may inscribe instead of the direct sizes their magnications,

choosing asuitable iriagniiication factor. This maybeV taken intoaccount, as Equation 3 shows, by displacing the second member of the circular slide rulel against the first member by a constant amount corresponding to twice the'logarithm'of the linear magnification.

. The 4varying sizes of the impression or their magnications will be represented on this member-as adouble curve bordering a spiral, the sides 32,7334, Figs. 2 and;4, of whichare functions of the logarithm of the area of, .or functions of twice the logarithm ,determining the linear dimension of the 'impression'.

Against this representation of the varying;sizes o f thegimpression .ori its magnification, the impression or itsimage is registered, the impression Y being'viewed normally vby a microscope, or its the two elements'. Y,

I I2', must now be correctly related or brought into correct spatial relationship to the values inscribed on the'first element or disc I, previously described, ofthe measuring apparatus. Y f

In` inscribing vthis first element a chosen constant size of impression was used to lay out .the

corresponding values of the load and hardness numerals, and this is the relating factor between 'The twoscales of disc `I, hardness scale21 and load scale 28, or their' respective originsy 3U, 37|',

are to be brought into a certain spatial relation- Y Y ship to,` or displacement against, the spiral 3,2, 33, or -Vits origin 44, which takes account of the chosen constant size of the impression which is also eX- pressed by the constant C ofthe apparatus, and which takes account furthermore of the magnification mof the optic system. These mutual rela-1 Y tionsof the valueslare. given by Equation 3 ywhich tells that in. order to read the hardness number H for a given loadfL` and afgiven impression d, the origin ofthe logarithmic representation. of the impression is tol beshifted against the given lo'adpoint for a length whichwcorresponds tothe logarithmic representation of. the .constant C of the apparatus and' theV chosen .magnification m.

If the magnication varied, thecorresponding Y displacement is' to be changed'Ihe twodis placements', one' with relation to the lcad point.

On the second mov-V As set forth yhereinbefore, for any givenr hardexecuted as one step,i'part1cularly lfthepphc lsystemis for-only one"magnlcati'on. Y e

itWe have l thus illustrated on 'disc A*2 of Tige-f2 ra=magnification indicator3'5 showing twoim'arkws 1A `and B,'themark A lbeings'etag'ain'st fthe load points, for example 2l/2 in Fig. 4, whenthe non Amal "magnification *fof 1 the Aoptic'system of'lig. 3 #isito-"be used. iAnyisetting-lof' th'ein'arkf-Afagainst any-:load point will vsii-nuitane'ou'sly'-"take iacc'ourlt of the displacement (2 log-'m5 necssaryforlfthe magnification.

If another magniffoat'ionl 'mmis to be'fused, We mayf'orinstancemake use, 1"instead'o'fvxnark A, of another mark B, the setting of this mark against a load point taking into account for the evaluation simultaneously of the changed magnification m and the load.

An embodiment of an evaluation apparatus is shown in Fig. 3. The disc is mounted on one end of a shaft 4 which carries at its other end a disc 5. Disc 5 is to be used for setting the displacement between discs I and 2 in accordance With the load used when making the impression and the magnification of the optic system. A knurled knob 6 is secured to disc 5 for rotating the shaft 4.

Disc 2 is mounted on a sleeve 1 which is freely rotatable about shaft 4. Discs 5 and 8 may be locked together in a spatial relationship deter-v mined by the load and the magnification as just has been described.

For this purpose, disc 5 is provided with a pin 9 which may enter any of a number of holes 55, disc 8 and disc 5 being pressed towards each other by means of a spring arranged on shaft 4, between discs I and 2. Discs I and 2 may then be rotated by means of knob 6.

On the circumference of disc 5 there may be inscribed the marks A and B, and the edge of disc 8 may carry a reproduction of the load scale not shown on the drawing. Since, however, disc 5 is solidary with disc I and disc 8 with disc 2, the sense of displacement between magnification indicator and load scale is to be reversed when` compared with the scale and indicator of Fig. 1 and Fig. 2. The indicator and scale are therefore to be reproduced on discs 5 and 8, respectively, as mirror images of the indicator of Fig. 2 and of the load scale of Fig. 1, or Fig. 4.

II is the test piece and I2 the visual mark or impression formed therein by the penetrometer (not shown).

The optic system for producing a magnified l image of the impression consists of a microscope objective I3, a vertical illuminator I4, a projection lamp I5, and a lamp condenser I6. y

The optic system for projecting an image o the impression I2` on the viewing screen I'I consists of a projection ocular I8 and a prism I9. The optic system for projecting an image of the relevant part 5I of the hardness scale 21 upon the viewin'g screen 20 consists of lamp 2l, condenser 22, projection lens 23 and prism 24.

Assuming that the impression I2 has been made on the test piece, the hardness number is obtained in the following manner:

The load, for inst-ance 21%3 and the magnication being known, the two discs I and 2 are suitably coupled together by means of pin 9 and the appropriate pole for instance that mark A points to the load point 2l/2. Both discs I and 2 are rotated by means of knob 6 until the image II2 of the impression I2 is exactly calipered in n'o't ylint-'erfere Iwith-each Jother. Since the margin I of "disc `-i containing the hardness fscale "projects overthe fcircn'ference of disc -2,`-=disc 2 LWi'1l`"no"t obscure or impede the passage of the pencil of rays of the optic system 2|, 22, 23.

The hardness number m-ay thus be read directly from disc 2 at 5I or from its projection on screen 20.

Let it be supposed that mark A is brought into coincidence with any given load and fixed in position by means of pin 9 and the appropriate hole 50. If now, the elements I and 2 are rotated together by means of the knob 6 until the logarithmic spiral 32-33 calipers the image of the impression I I2, the correct hardness numeral will be read oi from the outside of the larger disc against the datum line. In practice it is convenient as just has been pointed out to read these values olf at a point diametrically opposite to the impression, but this is only equivalent toproduc ing line 53-53 which intersects normally both the common axis 4I--4I of rotation of the movable elements I and 2 and the normal to the impression I2, or optic axis IU- 40, and transferring the graduations to the opposite side of this disc. Also in practice a spring pin location 9, 50, lll and connection between the two elements corresponding to each load is conveniently provided; the spring pin being conveniently located on the radius with mark A ofthe logarithmic spiral element and engaging with any one recess or hole in the other element when corresponding with any of the load values.

If the magnification is altered, this is equivalent to having to use on the logarithmic spiral instead of the radius with the mark A, another radius such as the one with mark B as has been described hereinbefore, and if a second spring pin in the appropriate position is provided to connect in a different relative position with the load values on the other movable element, the previous connection being rendered inoperative, the proper values of the hardness numerals for this magniflcation are indicated against the line 53-53 intersecting normally the common axis II I-4I of rotation and the optic axis l0-4D, and read off. If desired several such connections could be provided for different magnications.

Thus it will be seen that the hardness numerals are directly evaluated by a measuring apparatus constructed in accordance with the invention, under all the possible conditions of carrying out the measurement. v-

What we claim and desire to secure by Letters Patent of the United States is:

l. An apparatus for the direct numerical evaluation of hardness from the observation of an impression made on metals under a denite load by means of a penetrometer under specified conditions, comprising two coaxially mounted transparent discs, one oi said discs being suitably inscribed with logarithmic scales of corresponding values of the load and the hardness for a given constant size of impression, the other of said discswith a dqublesided equiansular. legalithmic spiral, the angular distances from a giyenorigin of said spiral representing on a logarithmic scale Y the squares of va determininglinear dimension vof saidvflirnpression and the segments of the radii between the sides of said spiral representing the lengthsof said dimension; said discs beingV adapted to be piyotally displaced against eachotherfor Y .bringing said scales on the one of said discs and said spiral o ntheY other of said discs into a denite spatial relationship depending on the load used. When'making sjaid impression; said doublesidedlogarithrnio spiral adapted to caliper said Y determiningV dimension, the 'calipering angular 4 aaaasl position indicating .91! the first .0i Said ,dises the hardness value of said meta1.`

2. An apparatus asset forth in clairn l'whrein interengaging locking means areA provided on -both Ysaid discs for interlockingsaid discs in various positions of said vspiral originrelatively to :said load scale. y Y Y Y 3. An apparatus asset forth in claim 1 wherein an optical system is lprovided for projecting anv image of said impression intorfocus in the plane of said doublesidedspiral. Y Y 

